What should sit beside a physics equation?

[samuel_a]

Hi all,

I’m working on a physics equation reference and I’m trying to make the sourcing and explanations as reliable as possible.

When you look up a physics equation, what do you most want alongside it: assumptions, units, variable definitions, derivation, worked example, limits of use, or something else?

I’d really value input from people who study, teach, or use this material regularly.

 

[symbolipoint]

Wildly guessing, thematize the equations according to textbook sections of a target book from which to be used for studying. One may state what each variable represents or the variables could be understood according to what is being studied. Would a published reference handbook do what you want?

 

[samuel_a]

Thanks, that makes sense. It is already organised quite heavily by topic, so that is useful confirmation for me. I think the next thing I am still trying to work out is what is most worth showing directly beside each equation rather than just in the wider topic structure.

 

[Borek]

It sometimes depends on what the equation is. There is at least one equation very often used in chemistry (so not physics, but I am sure physicists will have similar examples) that is nothing else but a rearranged basic equation describing acid dissociation - it is just that the rearranged version is much more convenient to use is practice (Henderson-Hasselbalch equation vs acid dissociation constant definition in case anyone wonders). There, the derivation (or some explanation of what is going on) is a must.

Other example I can think of is a Michaelis–Menten equation - which is basically a trivial modification of a basic kinetics equation. It seemed so obvious to me as an extension of a basic theory I was actually surprised to learn it is treated as a specific case worth of being named. Here, again, it is derivation that matters.

But in both cases basic equations - one for dissociation equilibrium and one for reaction kinetics - were discovered and used without any derivation (many, many years after discovery it was shown they can be derived either from thermodynamics or using statistical mechanics), so I wouldn't think of showing their derivations as something basic (worth of mentioning, definitely).

 

[Baluncore]

Take a look at a book of physics formulas.
https://www.amazon.com.au/dp/B0BDXFMG5M/

 

[ohwilleke]

When you look up a physics equation, what do you most want alongside it:

assumptions (yes),

units (yes),

variable definitions (yes),

derivation (no, the reason you have a reference is so you don't have to derive it),

worked example (good for a study guide, but not for a reference because it makes the reference too long),

limits of use (yes),

or something else (alternative names for the equation if there is more than one common name, a citation to a source for the entry and a citation for information about the person(s) it is named after if it is named after a person)